This is a side-affect of Pinstripe's "-moz-pulldown-menu" font in menulists (Classic had "message-box"). Basically, the font-size doesn't inherit from the parent that it used to do before bug 344570 was fixed. So if the parent has a small font, menuitems will look a bit odd with the big font. This doesn't affect Firefox, because afaik menulists in Firefox all have a large parent font. See also bug 349437. I haven't investigated how this hits other toolkit apps, though. There are several possibilities to solve the issue (make the font inherit again, use a larger font in general etc). I'm setting this to block bug 328887, mostly in order to keep track of the issue.

fwiw, the patch in bug 349437 will fix this.

Fixed by the toolkit/FF patch in bug 349437.